A conventional washing-drying machine is disclosed in Japanese Patent Application Non-Examined Publication No. 2001-129287, and has a structure as shown in FIG. 7. As shown in FIG. 7, suspended outer tub 3 is placed in cabinet 1 using suspension 2 which absorbs vibration. Inner tub 4 used for accommodating clothes (articles for washing or drying) is disposed in outer tub 3, and can rotate about the center of shaft 5 for washing and spin-drying (dehydrating). Agitator 6 is rotatably disposed on the inner bottom of inner tub 4, and agitates the clothes (articles for washing or drying). Fluid balancer 7 is disposed on an upper part of inner tub 4. Protrusion 9 for agitating is formed on a dishlike base having slope 8 at its circumference, whereby agitator 6 is formed. Motor 10 is disposed under outer tub 3 and coupled with inner tub 4 or agitator 6 via clutch 11 and shaft 5.
One end of heat exchanger 12 is coupled with the lower part of outer tub 3 via lower-accordion-hose 13, and another end of heat exchanger 12 is coupled with one end of air blower 14 for drying. Another end of air blower 14 is coupled with warm-air supplying pass 16 having heater 15, where heater 15 and air blower 14 form a warm-air blowing section. Pass 16 leads to inner tub 4 via upper-accordion-hose 17. As a result, warm air is circulated through warm-air circulating pass 18 in the washing machine, where warm-air circulating pass 18 is formed by the hoses, the pass and so on.
Outer tub cover 19 is disposed on an upper surface of outer tub 3. Warm-air-spouting opening 20, which is connected with upper-accordion-hose 17, is punched on cover 19. Inner lid 21 used for putting in or taking out the clothes is formed on cover 19. Cabinet cover 22 covering an upper surface of cabinet 1 has outer lid 23, operational display section 24 and water valve 25 for supplying water into inner tub 4. Drain valve 26 for draining water from outer tub 3 is disposed on the bottom of outer tub 3. Air blower 27 for cooling is disposed on the side of cabinet 1, and cools outer tub 3 and heat exchanger 12, which are placed in cabinet 1.
Controller 28, which includes a microprocessor, controls sequential processes i.e., washing, rinsing, dehydrating and drying. In the processes, controller 28 controls a drying process by inputting a detected output from thermistors 29 and 30, where thermistor 29 detects a temperature of an outer wall of heat exchanger 12, and thermistor 30 detects a temperature of circulating air at an exit of heat exchanger 12.
In the conventional washing machine discussed above, sequential processes i.e., washing, rinsing, dehydrating and drying are operated by the well-known method. The detailed descriptions of some processes i.e., washing, rinsing and dehydrating are omitted hereinafter, and only drying process is described.
In the drying process, drain valve 26 is closed, clutch 11 is shifted and rotating force of motor 10 is transmitted to agitator 6, so that the clothes are agitated by agitator 6. At the same time, warm air is sent to warm-air-spouting opening 20 using the warm-air blowing section formed of air blower 14 and heater 15, whereby drying is performed. As a result, water is evaporated from the clothes. Warm air including moisture produced from evaporation of water on the clothes moves from inner tub 4 to an inside of outer tub 3, then moves through lower-accordion-hose 13 and reaches heat exchanger 12. Since an inner wall of outer tub 3 or heat exchanger 12 is lower than the warm air in temperature, moisture condensation occurs, and moist warm air is dehumidified and returns to air blower 14. The clothes in inner tub 4 are dried circulating the warm air using warm-air circulating pass 18.
A temperature of circulating wind in the drying process changes as shown in FIG. 8. Firstly, when drying starts, a temperature of the clothes exposed to warm air increases during preheat period T1.
Secondly, inputting heat from heater 15 and latent heat of evaporating water included in the clothes achieve a state of equilibrium during period T2 referred to as a constant-rate period of drying. Then drying progresses further, and water adhered on a surface of the clothes evaporates completely.
Thirdly, water included within the clothes evaporates during period T3 referred to as a decreasing rate period of drying. Because the amount of latent heat of evaporating water becomes less than inputting heat from heater 15 during period T3, surplus inputting heat increases temperatures of the clothes and circulating wind, where a starting point of increasing a temperature is referred to as inflection point A1. Controller 28 determines inflection point A1 with a rate of change between detected temperature TH1 of thermistor 29 and detected temperature TH2 of thermistor 30. A drying rate of the clothes is approximately 90% through 95% at inflection point A1, so that a given delayed period is provided after inflection point A1 and clothes are enough dried. After that, the drying process finishes.
However, in the conventional washing-drying machine, warm-air circulating pass 18 is needed to form in a restricted space of cabinet 1, so that a sufficient cooling area for heat exchanger 12 can not be obtained. As a result, a high dehumidification rate can not be achieved, and a drying time tends to be longer. Air-cooling method mentioned above, which cools indirectly warm air circulating in heat exchanger 12, needs a large heat-exchange-area and is difficult to obtain a high cooling capacity. In addition to that, the conventional washing-drying machine as shown in FIG. 7 is difficult to agitate even a small amount of clothes, because of a top-loading type. Besides, when inner surface of inner tub 4 and outer tub 3 are wet, a time from a starting of a drying process to increases of temperatures of inner tub 4 and wet clothes in inner tub 4 becomes longer. As a result, drying becomes difficult to be detected, and drying efficiency deteriorates, so that the drying period becomes longer.
In the conventional washing-drying machine above mentioned, humidity of warm air circulating in heat exchanger 12 reaches approximately 100% during the constant-rate period of drying. However, warm air is not dehumidified by only the air-cooling method and circulates. In addition, heat-exchanging efficiency does not reach a higher level because of retention of moisture condensation adhered on an inner wall of heat exchanger 12. As drying progresses during the decreasing rate period of drying, a temperature of circulating wind increases, so that clothes, which are made of chemical fibers or the like and therefore dry fast, are over-dried. As a result, wrinkles occur in the clothes or clothes easily become damaged.
When a cooling section of heat exchanger 12 is stopped or efficiency of the cooling section deteriorates in the drying process due to trouble, the drying time is prolonged and the clothes are likely to be damaged. In this case, process time of agitating clothes by using agitator 6 becomes longer, so that wrinkles and entanglements are likely to occur in some clothes. In addition to the problem discussed above, the conventional washing-drying machine (either air-cooling method or water-cooling method) has problems, which are spending a lot of energy and amounts of water.